Commercial sensors, such as reflective sensors which detect the range of a reflective surface are generally manufactured in large quantities at very low cost. The range within which a sensor of this type may detect the proximity of the reflective surface is generally a few millimeters for low-end commercial devices. Typically, the response characteristics are non-linear meaning that a low signal condition exists where the distance between the sensor and the reflective surface is more or less than the optimum for maximum signal strength.
An example of art that discloses a mechanical sensing mechanism is U.S. Pat. No. 5,917,180, Reimer, et al. This patent describes an integrating cavity sensor that incorporates a light emitter and light detector positioned in close proximity and uses mechanical deformation of the integrating cavity to sense deflection. Deflection sensing is possible whereby an isotropic scattering medium surrounding the light source and detector act as an integrating cavity. It is a property of the medium that compression of the whole body results in proportional compression of the localized region that is the integrating cavity which in turn changes the optical density of the medium proportionate to the deflection of the medium. Due to this proportionality, this sensor can be configured to sense deflection on an arbitrary distance scale by simply changing the dimension of the scattering medium. In the above reference, the medium is an elastomeric foam which provides the proportional compression.
The purpose of the present invention is therefore to provide an mechanical sensing arrangement for use in applications such as crash detector sensors, and other like uses.
In automotive crash sensing a number of devices are used or suggested for the detection of compression or deflection of the ‘crush zone’ or ‘crumple zone’ of the car. These devices include contact switches, fiber optic deflection sensors, Kinotex™ deflection sensors, air pressure sensors, etc. In these sensing devices it is desirable to match the deflection range of the sensor to a scale that matches the physical deformation scale of the crushing.